It has been conjectured that the primary cause of roughness of silicon surfaces etched in KOH is random masking of the silicon surface by the H2 bubbles produced in the reaction. In order to test this model, we have observed and measured bubbles occurring during (100) silicon etching in aqueous KOH solutions. We have confirmed the trends for the average bubble departure radius Rd and average dwell time Td noted by previous authors under different circumstances: Td invariably decreases for increasing temperature and concentration and Rd decreases with increasing concentration and flow speed. Two distinct kinds of topography result from the hour long etch. A region that was covered by bubbles looks like a superposition of shallow depressions, with lateral radii comparable to the bubble departure radius and roughness consistent with a pseudo-masking model . Therefore the roughness is dominated by the effect of bubbles and determined by bubble parameters if when and where those do occur. A different roughening regime, resulting in hillocks, is reached by decreasing Td and bubble density (for instance by increasing flow speed). Depending on the parameters bubbles do not occur over all the surface being etched, or do not occur at all.